How would you calculate rolling circumference?

[Matt UK]

Just looking at tyre / wheel size combos for the Caterham.

I've done my maths but when I put a tape measure to the car it's not even close.

So, indulge me. How would you work it out?

Tyre is a 185/60 R13.

I made it 1736mmm rounded.

[rovsd1]

This may help.
http://www.carbibles.com/tyre_bible_pg4.html
Regards Ged

[aeropilot]

1684mm according to this...

http://www.club80-90syncro.co.uk/Syncro_website/Te...

[D_G]

Tyre width / ratio give you the tyre height, then x 2. Times wheel size by 25.4 to get mm. Add two together and times by pi.

You are pretty close.

[Egg Chaser]

13inch = 330.2mm

185 x 0.60 = profile = 111mm x 2 = 222mm

330.2mm + 222mm = 552.2mm overall diameter

circumference = pi x diameter = 3.14 x 552.2 = 1733.9mm

[ROOODBOY]

Why not just jack the car up, put some string around the tyre and mark it at one full revolution, remove string and measure it.

It will vary a few percent due to tyre wear.

[Mr Sparkle]

3.14((13 * 25.4) + 2(0.6 * 185)) = 1734mm

[johnoz]

I use this....

http://www.miata.net/garage/tirecalcold.html